Certain nonlinear radio frequency (RF) circuits become unstable as RF power of an input signal increases. Bode's stability theory addresses return ratio, return difference and Nyquist criteria in linear networks at DC operating points, but does not provide similar information for nonlinear RF circuits operating at finite RF input powers. When designing nonlinear RF circuits, it may therefore be difficult to determine stability margins and to predict and/or simulate stability of a proposed RF circuit at various RF powers.
Accordingly, there is a need for a solution capable of verifying stability at arbitrary RF power, enabling assessment of gain and phase margins, and locating unstable portions of the RF circuits.